1. The Field of the Invention
The present invention relates to obstetrical instruments and methods. Specifically, the present invention relates to a vacuum extractor that regulates traction force.
2. The Prior State of the Art
One need not be a parent to realize the importance of improved medical devices and methods in delivering a fetus safely into this world. Currently, there are two major methods for delivering a fetus, the Cesarean section delivery and the vaginal delivery.
In Cesarean section deliveries, the fetus is delivered through an incision made in the uterus and a corresponding incision made in the abdomen. An upward-pulling force is required in order to pull the fetus through the incisions and out of the mother. Often, the force is provided by the childbirth attendant""s hands directly pulling the fetus through the abdominal incision.
In vaginal deliveries, the fetus is delivered through the vaginal passage after the cervix has fully dilated and effaced. Passing the fetus through the vaginal passage requires that the vaginal muscles be forced to stretch because the fetal head is much larger than the vaginal passage under normal circumstances.
Some stretching force is applied to the vaginal tissues by the mother herself. The involuntary contractions of the uterus during labor push the fetus (typically the fetal head) into the vaginal passage to stretch the vaginal tissues. The stretching force of these involuntary uterine contractions is combined with the stretching force caused by voluntary contractions of the mother""s abdominal muscles as the mother tries to push the fetus out of the uterus.
Often, the forces described above are not strong enough or are not medically advisable to use in extracting the fetus. Supplementary force may be applied with a fetal vacuum extractor, for example, in conditions of dystocia (i.e., slow or difficult labor or delivery), uterine inertia, maternal exhaustion, maternal distress, or fetal distress.
In a conventional fetal vacuum extractor, a vacuum cup is sealed over a portion of the fetal head (e.g., the occiput). A flexible tube connects the vacuum cup to a vacuum pump operated by a secondary operator such as a nurse. The vacuum pump allows the nurse to provide a vacuum within the vacuum cup, thereby creating suction between the fetal head and the vacuum cup. As long as a sufficient vacuum is maintained, the primary operator, such as a physician, may pull on the vacuum cup handle, thereby applying traction (i.e., a pulling, delivering force) to the fetal head.
The convention fetal vacuum extractor is useful in providing traction to the fetal head. However, the magnitude of the traction force needs to be controlled for the duration of the contraction. If the traction force is too weak, the force will be insufficient to significantly assist in childbirth. However, if the traction force is too strong, the fetus or the mother may be subject to a higher risk of injury.
Historically, traction forces as high as fifty pounds have been used to extract the fetus. However, recently, there have been reports of fetal compromise such as subgaleal hematomas causes by excessive traction force. Specifically, excessive traction forces can dislodge the scalp from its periosteal surface breaking capillaries and blood vessels.
Proper use of the vacuum extractor is dependent principally upon the proper application of the vacuum cup to the fetal head. When the vacuum cup is placed upon the flexion point (three centimeters forward of the posterior fontanelle along the sagittal suture) of the fetal head, the least diameter of the fetal head is presented through the birth canal. This causes less resistance and, therefore, lower traction forces are required to assist in fetal vaginal deliveries where vacuum cups are used.
Typically, a traction force of approximately twenty pounds is all that is needed to assist in vaginal deliveries if the vacuum cup is properly applied. However, more or less traction force may also be appropriate as determined by a licensed, medically competent childbirth attendant. The major determinant is that progress of the fetal head descent is made with each contraction.
Currently, childbirth attendants typically estimate the amount of traction force being applied by sense of touch. In other words, the childbirth attendant by experience determines whether the amount of traction force is too great, too small, or acceptable. While childbirth attendants, and particularly physicians, are typically competent to judge what is an acceptable amount of traction force, even physicians may often misjudge the amount of traction force being applied. In the case of a misjudgement, the traction may be insufficient to assist in childbirth, or the traction may be great enough to cause injury to the fetus or mother.
Therefore, what is desired is a system and method for providing information regarding traction force while the childbirth attendant is using a vacuum extractor for use in childbirth.
The present invention includes a vacuum extractor for use in childbirth. The primary function of this vacuum extractor is to apply traction force to the fetus (typically the fetal head) when the natural force provided by the mother is insufficient or inadvisable to use in completing childbirth. A childbirth attendant will typically be educated as to the amount of traction force that may be safely and effectively applied to the fetus. Typically, the childbirth attendant will judge the amount of traction force by sensing how much force he or she feels is being applied.
The present invention provides a mechanism where a childbirth attendant can objectively know the amount of traction force being applied. Specifically, a force sensor is coupled to the vacuum cup. The force sensor indicates the amount of traction force to the childbirth attendant. The force sensor may include a gauge that allows the childbirth attendant to visually determine the amount of force being applied. For example, a spring in the mechanism may compress in response to traction force, causing the position of a marker connected to the spring to change. The traction force may thus be determined by comparing the position of the marker with a scale provided on the force sensor.
The force sensor may also include a slipping mechanism whereby the childbirth attendant feels when a predetermined level of traction force has been exceeded. Specifically, when the predetermined level of traction force is exceeded, the length of the force sensor suddenly increases or slips, for example, approximately one inch. This slipping can be easily felt by the childbirth attendant. At this point, the childbirth attendant may choose to continue traction. Alternatively, the childbirth attendant may discontinue traction, causing a restoration mechanism to return the vacuum extractor to its unslipped position.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.